Low oil pressure fixe by... changing oil?

[Anduril]

Wife's 1999 Cavalier (2.2, 230k miles) was getting a low oil pressure light at low idle on a cold engine. When she first started the car, it seemed to take a bit longer than normal for the light to go off with the engine idling fast, and when the idle slowed down but the oil hadn't fully warmed up, the light came on. Giving it the slightest amount of gas caused it to go off.

Fearing the worst, I changed the oil. The level was within 1/4 of a quart of full before I drained it (car has always had a small leak) and I used the same weight of oil. The only difference was I had tried Valvoline MaxLife for its supposed ability to clean up an engine and seal leaks (it didn't) and refilled with Rotella. Perhaps the MaxLife had done some cleaning after all and partially clogged the filter, which I replaced? Since changing the oil, the light has not come back on, and the car builds pressure almost immediately on starting. I always thought low oil pressure was a sign of worn out bearings or oil pump, though. Not that I'm complaining about what was apparently a simple fix, I'm just wondering why it worked.

 

[tomcat27]

fresh, slightly thicker oil? have the old oil analyzed and you will likely find diluted and/or sheared oil. most likely diluted?

 

[FordBroncoVWJeta]

My Sunfire with the same engine has the same problems. Its actually quite common on the 2.2. Mine does it when you have been driving for a while and come to a complete stop, light comes on. Then barley touch the gas it goes off. I think it is because the idle is so low on these cars. My car seems to idle at like 600RPMs.

 

[Anduril]

Originally Posted By: tomcat27
fresh, slightly thicker oil? have the old oil analyzed and you will likely find diluted and/or sheared oil. most likely diluted?

Oil is already gone, but wouldn'tthat be the exact opposite of what was happening? Low pressure when the oil was cold and at its thickest, and good pressure as it warmed up and thinned out.

 

[Lubener]

You got other issues if your oil was diluted that much. I would bet your oil pressure is marginal at best. Maybe your sending unit is going bad.

 

[demarpaint]

If the oil was diluted that could explain the lower pressure. I have a feeling something is wrong. I'd get a mechanical oil pressure gauge and check oil pressure now, and again at the end of the OCI, or next time the light comes on. I would also get a UOA to rule out fuel dilution, and dig in further if needed once I had the above information. It could be something as simple as a bad sending unit.

 

[supton]

I agree, get a mechanical readout for the actual pressure (although if it's cheap enough it may be worthwhile to shotgun the pressure sensor).

How do you know the Maxlife was not cleaning? Or do you mean that it did not fix any oil leaks? Curious, as I have Maxlife in mine, and it picked up a valve cover gasket leak while using it.

I have cut open the oil filters on mine, it's a pain but it's doable, with a vice and a hacksaw and a screwdriver. I score around the filter, near the end with threads on it. Careful: the OEM filter has "thick" metal, and the Carquest one I did was quite thin. I score, then make one cut that goes through. Then I work the opening around with a screwdriver. Warning: the OEM filter retains oil pretty good, even over night. As a result expect a fair amount of oil (the Carquest filter did not have any oil in it).

 

[Donald]

Originally Posted By: Anduril
Wife's 1999 Cavalier (2.2, 230k miles) was getting a low oil pressure light at low idle on a cold engine. When she first started the car, it seemed to take a bit longer than normal for the light to go off with the engine idling fast, and when the idle slowed down but the oil hadn't fully warmed up, the light came on. Giving it the slightest amount of gas caused it to go off.

Fearing the worst, I changed the oil. The level was within 1/4 of a quart of full before I drained it (car has always had a small leak) and I used the same weight of oil. The only difference was I had tried Valvoline MaxLife for its supposed ability to clean up an engine and seal leaks (it didn't) and refilled with Rotella. Perhaps the MaxLife had done some cleaning after all and partially clogged the filter, which I replaced? Since changing the oil, the light has not come back on, and the car builds pressure almost immediately on starting. I always thought low oil pressure was a sign of worn out bearings or oil pump, though. Not that I'm complaining about what was apparently a simple fix, I'm just wondering why it worked.


I saw a clogged Amsoil oil filter cause odd things including the oil pressure light.

 

[Anduril]

If it happens again, I'll investigate further. The oil pressure sender, just like the oil filter, is in a horrible location on this vehicle so I'd rather leave that alone for now.

For the MaxLife, I mean it still leaks just as much after a 5k OCI as it did beforehand. No idea if it cleaned anything or not but it didn't stop the leak.

 

[sleddriver]

Originally Posted By: Anduril
....I always thought low oil pressure was a sign of worn out bearings or oil pump, though. Not that I'm complaining about what was apparently a simple fix, I'm just wondering why it worked.
Old o-rings in the pickup tube could have shrunk, causing a loss of vacuum. Therefore your oil pump might be cavitating.

Just a guess.....